Weeds cause tremendous global economic losses by reducing crop yields and lower crop quality. Worldwide agronomic crops must compete with hundreds of weed species. Herbicides, used to combat these weed species are now standard technology on farms and ranches. The proper agronomic use of herbicides results in increased crop yields and quality and, concomitantly, increases production and harvesting efficiency.
In spite of the commercial herbicides available, damage to crops caused by weeds still occurs. In addition, often herbicides do not provide a sufficient margin of safety for the crop, thus damaging the crop as well as the weeds. Accordingly, there is an ongoing need to create more crop-selective as well as more effective herbicidal agents.
Thiochroman and dihydrobenzothiophene (DHBT) herbicidal agents are described in U.S. Pat. No. 5,607,898 and WO 97/08164. However, none of the compounds described therein contain a thiono moiety.
It is therefore an object of the present invention to provide thiono-thiochroman and thiono-dihydrobenzothiophene compounds which demonstrate herbicidal activity in conjunction with crop safety.
The present invention provides a herbicidal compound of formula I 
wherein m is zero or 1;
R1, R2, R3 and R4 are each, independently, H, C1-C4 alkyl, C1-C4 haloalkyl or C2-C4 alkoxyalkyl;
R5 is C1-C3 alkyl, C2-C4 alkenyl, or C2-C4 haloalkyl;
R6 is H, halogen, CN, NO2, C1-C4 alkyl, C2-C4 alkenyl, or C2-C4 alkoxyalkyl.
X is O or S(O)n;
n is zero, 1 or 2;
Y is CR7R8, CHOR9, C(OR9)2, Cxe2x95x90NOR10, Cxe2x95x90O or Cxe2x95x90NNR20R21;
R7 is H, C1-C4 alkyl or C1-C4 haloalkyl;
R8 is H, C1-C4 alkyl or C2-C4 alkenyl or C2-C4 alkenyl;
R9 and R10 are each, independently H, C1-C6 alkyl optionally substituted with one or more halogen, C1-C4 alkoxy, C2-C6 alkenyl, C2-C6 alkynyl, C1-C6 haloalkyl or C3-C6 cycloalkyl groups, or when two R9 groups are present they may be taken together with the atoms to which they are attached to form a five- or six-membered ring;
Q is H, SO2R11, COR12, CO2R13, P(O) (OR14)2 or C1-C4 alkyl optionally substituted with COR15, CO2R16, P(O) (OR17)2 or phenyl optionally substituted with one to three halogen, NO2, C1-C4 alkyl, C1-C4 alkoxy or C1-C4 haloalkyl groups;
R11, R13, R14, and R17 are each independently C1-C8 alkyl, C3-C8 cycloalkyl, or phenyl, optionally substituted with one to three halogen, nitro, C1-C4 alkyl, C1-C4 alkoxy or C1-C4 haloalkyl groups;
R12 and R15 are each independently H, NR18R19, C1-C8 alkyl, C3-C8 cycloalkyl or phenyl optionally substituted with one to three halogen, NO2, C1-C4 alkyl, C1-C4 alkoxy or C1-C4 haloalkyl groups;
R16 is H, C1-C8 alkyl, C3-C8 cycloalkyl or phenyl optionally substituted with one to three halogen, NO2, C1-C4 alkyl, C1-C4 alkoxy or C1-C4 haloalkyl groups;
R18 and R19 are each independently H or C1-C6 alkyl;
R20 and R21 are each independently H or C1-C6 alkyl or R20 and R21 may be taken together with the atom to which they are attached to form a five- or six-membered ring;
Z is H, halogen, C1-C4 alkyl, C1-C4 haloalkyl, C2-C4 alkoxyalkyl, C1-C4 alkoxy or C1-C4 haloalkoxy; and
p is zero, 1, 2, or 3; or
the agriculturally acceptable salts thereof.
Also provided are herbicidal compositions and methods and a process for the preparation of the Formula I compound.
The term safety or selectivity in weed science refers to the characteristic by which undesirable species of plants (weeds) are killed or seriously injured in the presence of desirable plant species (crops) without concomitant injury of the desired plant species. The use of herbicides frequently causes a varying degree of crop injury. Such crop damage is a problem that generates a continuous need for more selective herbicides worldwide. This is especially true of crops such as cereals which are often unacceptably damaged by herbicides designed to protect said crops against invasive weeds.
Surprisingly, it has now been found that the formula I compounds of the invention demonstrate good herbicidal efficacy against undesirable plant species along with enhanced crop selectivity. In particular, the formula I compounds of this invention are surprisingly safe in cereal crops such as corn, wheat, rice, or the like, preferably corn.
Compounds of the invention have the structural formula I 
wherein R1, R2, R3, R4, R5, R6, Q, X, Y, Z, m and p are described hereinabove.
The term halogen as used in the specification and claims designates chlorine, fluorine, bromine or iodine. The term haloalkyl designates an alkyl group, CnH2n+1 which may contain from one halogen atom to 2n+1 halogen atoms. Similarly, the term haloalkoxy designates a OCnH2n+1 group which may contain from one to 2n+1 halogen atoms. Haloalkenyl designates an alkenyl group CnH2n which may contain from one to 2n halogen atoms. In each instance the halogen atoms may be the same or different.
The formula I compounds of the invention include all stereoisomeric and regioisomeric embodiments.
The agriculturally acceptable salts of formula I include salts such as alkali metal, e.g. lithium, sodium or potassium; alkaline-earth metal, e.g. calcium or magnesium; ammonium or amine, e.g. diethanolamine, triethanolamine, octylamine, morpholine, dioctylmethylamine or any of the conventional salts suitable for use in standard agricultural practice.
Preferred compounds of the present invention are those formula I compounds wherein X is SO2; Q is H; and Y is CR7R8, CHOR9, C(OR9)2 or Cxe2x95x90NOR10.
Compounds of formula I, wherein Q is hydrogen, may be prepared from the corresponding ketone by treatment of said ketone with Lawesson""s Reagent in the presence of a solvent, preferably an inert solvent such as dimethoxyethane. The reaction is shown below in Flow Diagram I.

Lawesson""s reagent may be represented by the structure shown below and is available commercially. 
Compounds of formula I in which Q is SO2R11 may be prepared by treating the formula I compound wherein Q is hydrogen with a suitable sulfonating agent,R11SO2halide, in the presence of a base, preferably potassium carbonate. The reaction may be conveniently carried out in a two-phase solvent system in the presence of a phase-transfer catalyst such as benzyltriethylammonium chloride (BTEAC). The reaction is shown in Flow Diagram II, wherein the sulfonyl halide is a sulfonyl chloride.

Compounds of formula I wherein Q is is other than H or SO2R11 may be prepared in a manner similar to that described in U.S. Pat. No. 5,607,898 or in WO 97/08164.
Advantageously, it has now been found that the formula I compounds of the invention are particularly useful for the selective control of undesirable plant species in the presence of crop plants, seeds or other propagating organs. In particular, the compounds of this invention are selective in cereal crops such as corn, wheat, rice or the like, preferably corn.
In actual practice, the compounds of the invention may be applied to the foliage of undesirable plants or to the soil or water containing seeds or other propagating organs thereof, preferably to the foliage, in the form of a solid or liquid herbicidal composition. Said composition may take the form of an emulsifiable concentrate, a concentrated emulsion, a wettable powder, a soluble granule, a suspension concentrate, a flowable concentrate or any convenient conventional form useful for herbicide application.
The composition of the invention comprises an agronomically acceptable inert solid or liquid carrier and a herbicidally effective amount of a compound of formula I. The herbicidally effective amount of the formula I compound may vary according to the prevailing conditions such as weed pressure, crop species, application timing, form of application, soil conditions, weather conditions or the like. In general, hebicidally effective amounts may be obtained when the composition of the invention is applied at rates of about 0.001 kg/ha to 10.0 kg/ha, preferably about 0.003 to 0.50 kg/ha, more preferably about 0.006 to 0.20 kg/ha.
The composition of the invention may be applied in combination with other herbicides such as dinitroanilines, for example trifluralin, pendimethalin or the like, preferably pendimethalin; triazines, for example atrazine, cyanazine, metribuzin or the like; AHAS inhibitors for example imidazolinones, sulfonyl ureas or the like; protox inhibitors; or any of the commonly employed, commercially available herbicidal agents. Said combination may be applied sequentially or concurrently as a tank-mix or co-formulation. Compositions of the invention embrace compounds of formula I alone or in combination with a second herbicide as active ingredient, preferably pendimethalin.